1. Field of the Invention
This invention relates generally to magnetic core storage memory systems and more particularly to a magnetic core storage memory system wherein the memory cores are bonded flat to specially designed carrier planes. These carrier planes are then stacked, forming a three dimensional array which is wired with X and Y drive lines and with either a combined sense/inhibit line or separate sense and inhibit lines.
2. Description of Prior Art
The rectangular hysteresis loop properties of magnetic cores are widely known and employed for fabricating binary storage devices. A basic core storage device consists of a matrix of toroidal cores arranged in rows and columns. All cores in a given row are wired by a common conductor to provide a single turn winding through each core. Similarly, all cores in a given column are wired by a common conductor. The two sets of conductors are referred to as the X and Y drive lines.
To store a binary 1 in a selected core of a typical storage device, the X and Y drive lines which coincide at the selected core are each energized with a current of half the magnitude necessary to set the core to the one state. All of the other cores common to the energized X and Y drive lines are disturbed but not set to the one state since each is subjected to a magnetomotive force of half the value necessary to set it to the one state.
To read the binary digit stored in a selected core, the X and Y drive lines which coincide at the selected core are each energized with half the current required to change the state of the selected core but in a direction opposite to that for storing a binary digit 1. If the selected core is storing a binary digit 0, it is not disturbed by the coincident currents. However, if a binary digit 1 is stored in the selected core, the state of the core is shifted from one stable state to its other stable state. The change is then sensed by a third line commonly referred to as a sense line.
A single matrix of magnetic cores may be employed to store or read only one binary digit at a time since only one set of X and Y drive lines may be energized at the same time. Accordingly, to provide a magnetic core storage device capable of handling groups of binary digits simultaneously or in parallel, a plurality of such magnetic core matrices often called core planes must be provided, one for each binary digit of a group to be stored or read out simultaneously or in parallel. Such a group is hereby defined to be a word of memory.
In such a three-dimensional arrangement for parallel storing and reading a group of binary digits, the corresponding X and Y drive lines of each core plane are connected in series and to corresponding X and Y current drivers. The separate sense line provided in each plane senses the magnetic flux in its plane of the selected core as it is shifted from one state to the other upon reading out a binary digit 1 stored therein.
To store a group of digits in the same memory location or group of cores, one in each plane, currents are passed through the X and Y drive lines in directions opposite the current directions for reading. However, the coincident currents through the corresponding cores of each plane in the three-dimensional array would switch all cores to the one state. To inhibit the storage of a binary digit 1 in the cores of selected planes, an inhibit winding is provided in each plane through which current is selectively driven in a direction opposite to either one of the coincident currents in the X and Y lines.
The method of packaging the memory described is commonly referred to as the stacked array. This method has been largely supplanted by the planar array and the folded planar array. The planar array and the folded planar array are arranged so that each core plane is capable of handling groups of binary digits simultaneously or in parallel. To describe its arrangement in other terms, the core plane is designed to contain complete sets of words; the words being composed of bits, with a bit being defined as a single core. The planar array or folded planar array core plane is, therefore, required to be designed with a specified word length in mind. Each time a new word length is desired a new design of core plane must be employed. If the memory capacity is to be increased, additional core planes are added.
The stacked array or the cubic approach, as it is sometimes referred to, lends itself to more economical inventory maintenance for a manufacturer of core memories by utilizing common core planes as building blocks. The manufacturer is able to design a single core plane. Each time a memory with a different word length is needed, a number of core planes equivalent to the number of bits in the specified word need be provided. However, as industry adopted the logic card approach to design of electronic products, the stacked array became obsolete. The stacked array geometry did not lend itself to the dimensional constraints of the logic card. Another reason for its obsolescence was the fact that the geometry of the planar and folded planar arrays resulted in a more efficient stringing or wiring process. More cores can be wired in a planar array with each pass of the needle used in the stringing operation than with a stacked array. Since stringing is one of the most costly aspects of core memory fabrication, industry was clearly predisposed towards the planar array, notwithstanding the dimensional constraints established by the logic card approach to packaging electronic products.
Increased densities were achieved with the planar array by manipulating the core angle relative to the drive lines. The folded planar array further increased the effective density by utilizing the volume around the core arrays.
Both the stacked array and the planar method of packaging core memories utilize cores which are placed perpendicular to the core carrier surface. These cores are arranged in their desired position by means of a core loading plate. The process of loading cores so they are perpendicular to the core carrier surface causes a high incidence of damage or stress to the cores during the core loading or transferring cycles, the result of which is a lower manufacturing yield.
The cubic magnetic core storage memory system of the present invention places cores flat to the core carrier surface, thereby reducing the damaging effects of present methods of core loading. The memory system of this invention allows increased word lengths without redesign of the core plane by simply increasing the quantity of core planes for any module or array. The present invention results in an increased effective density of memory elements over planar techniques.
Just as the logic card method of packaging electronics dictated the use of planar techniques over the use of the stacked array, the geometry of the integrated circuit modules of today are dictating a new geometry for core memory systems. The present invention is of the same geometric configuration as that of the integrated circuit module. The stacked array and the planar techniques do not lend themselves to the integrated circuit geometry, since the height of a stacked array is much greater than that of typical integrated circuit packages while the height of a planar array is much less.
The stringing of the present invention is far more economical than with any of the present memory configurations. One of the reasons for the increased economy is due to the fact that the cores are not placed at 40.degree.-45.degree. to the axis of the X drive line and Y drive line. Therefore, when stringing these lines the stringing needle has a larger aperture target because it will see the full inside diameter of each core. This results in fewer instances where the needle hits the core rather than the core aperture.